1. Field of the Invention
This invention relates to a process for polymerizing vinyl ethers, and, more particularly, to a new and improved initiator for effecting such polymerization in an efficient manner.
2. Description of the Prior Art
Polymers of vinyl ethers and catalytic processes to prepare these polymers have been described in the art. See U.S. Pat. Nos. 3,228,923; 3,365,433; 3,394,116; 3,461,075; 3,819,596; 5,055,536; 5,691,430 and 6,235,859. Various heterogeneous initiators or catalysts such as molecular sieves and zeolites have been used as the initiator system. Vinyl ethers also have been polymerized in the presence of strong Lewis acids such as boron trifluoride. Recently, J. Dougherty et al., in U.S. Pat. No. 5,691,430, disclosed a useful heterogeneous initiator system for polymerizing vinyl ether monomers. The catalyst was sea sand which contained predominately silicon dioxide and one or more metallic oxides. The vinyl ether homopolymer obtained had an advantageous weight average molecular weight and polydispersity.
U.S. Pat. No. 6,235,859 also described a process for polymerization of a vinyl ether monomer which employed an acid-treated acid clay mineral as catalyst. This acid treatment was intended to give the acid clay mineral a porous structure and a large surface area, which properties were considered advantageous for rapid polymerization of the vinyl ether monomer.
Accordingly, it is an object of this invention to provide a process for making vinyl ether polymers in a substantially quantitative yield.
A specific object herein is to provide such a process using an initiator which enables the polymerization to proceed at a predetermined reaction rate under advantageous temperature conditions.
These and other objects of the invention will be made apparent from the following description of the invention.
What is described herein is a new and improved process for producing a polymer of a vinyl ether monomer which comprises contacting the monomer with phosphorous pentoxide as the polymerization initiator.
Suitably, the phosphorous pentoxide initiator is present in an amount of at least 0.1 ppm, preferably 0.2-40 ppm, based on the weight of the vinyl ether monomer.
The phosphorous pentoxide initiator can be used neat, or with diluent, such as polyethylene, on or in a substrate, or contained in occurring mineral ore or clay, which ordinarily usually includes silicon dioxide and one or more metallic oxides such as aluminum oxide, magnesium oxide, ferric oxide or titanium oxide. The phosphorous pentoxide suitably is present in the ore in an amount of at least 100 ppm, preferably 200-4000 ppm. At least 10 mg of ore is used/g vinyl ether monomer for the polymerization. Suitably, such ores have a desirable porosity so that the ore is accessible to the monomer, suitably about 0.9 cc/g.
In this invention, polymerization of the vinyl ether monomer is substantially complete within 16 hours at a temperature ranging from room temperature to 55xc2x0 C. in a batch process; preferably within 2-12 hours at a temperature of 35-50xc2x0 C.